JPH07165949A - Prepreg with high dielectric constant and laminated board - Google Patents

Abstract

PURPOSE:To obtain the prepreg consisting mainly of a thermosetting resin, a fibrous reinforcing material and specific inorganic powder, developing no separation of the resin from the inorganic powder, excellent in appearance and dielectric constant uniformity, and causing no blisters and interlaminar debonding in its soldering process, thus useful for e.g. printed wiring boards. CONSTITUTION:This prepreg is made up from, as the chief components, (A) a thermosetting resin such as an epoxy resin, (B) a fibrous reinforcing material such as a glass cloth, and (C) inorganic powder composed of high-dielectric constant ceramic powder such as titanium dioxide powder and finely particulate powder <=0.1mum in average particle diameter such as anhydrous silica fine powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg for bonding layers of a multilayer board and a laminated board using the prepreg.

[0002]

2. Description of the Related Art Due to the miniaturization and high density of electronic equipment, multilayer boards have come to be often used for printed wiring boards. By providing a layer having a high dielectric constant in the inner layer of this multilayer board, the conductor width can be further reduced and the wiring density can be increased. Further, by positively utilizing this layer as a capacitor, for example, a stray capacity of a circuit conductor allows a high frequency component to flow to the ground layer as a bypass capacitor, or a conductor can be used as a capacitor (C) or an inductance (L) and can be further resistive by a printing resistor. By forming (R) and forming C, L, and R on the inner layer surface, the mounting density can be improved.

In order to provide a layer having a high dielectric constant on the inner layer of a multilayer board or a substrate, there are disclosed in Japanese Patent Laid-Open Nos. 55-57212 and 61-61.
As disclosed in Japanese Patent Publication No. 136281 and Japanese Patent Publication No. 5-415, a high dielectric constant ceramic powder such as barium titanate is mixed in a resin composition such as an epoxy resin or a modified thermosetting polyphenylene ether resin. A plurality of prepregs obtained by impregnating a fiber reinforcing material such as glass cloth and drying are stacked, copper foil is laminated on the outermost layer, and compression molding is performed by pressing to manufacture a copper-clad laminated substrate. Then, the obtained substrate is subjected to circuit formation by etching to be used as an inner layer core substrate, and a multilayer board is manufactured through a prepreg mixed with high dielectric constant ceramics or a prepreg not mixed.

[0004]

Although there are many cases in which a high dielectric constant substrate is used as an inner layer core substrate, recently, a demand for using a high dielectric constant prepreg for interlayer connection of a multilayer board has increased. . What is required of this prepreg is that the conductor circuit of the inner layer core substrate must be filled with the prepreg. This property is called the interior circuit filling property. Also, the adhesion between the resin of the inner layer core substrate and the conductor must be good.

However, since the prepreg having a high dielectric constant contains a large amount of ceramic powder having a high dielectric constant in a resin, it has a small amount of resin, poor fluidity and poor adhesiveness. Since it could not be filled, a void was generated, and there was a problem that blistering and interlayer separation occurred in the soldering work in the subsequent process, and the interior circuit filling property was poor. As a countermeasure against these problems, the amount of ceramic powder added may be reduced to increase the amount of resin that contributes to fluidity and adhesion. However, a multilayer board using a prepreg produced by using ceramic powder with a high dielectric constant and a reduced amount added When a substrate or a substrate is molded, there is a problem that the resin and the ceramic powder are separated. Separation of the resin and the ceramic powder occurs mainly in the peripheral portion (edge) of the copper-clad laminated board obtained by laminating copper foil on both surfaces of one prepreg and press-molding. In addition, when this prepreg and copper foil are laminated on both sides of the inner layer core board and press-formed to make a four-layer board, the location where the copper foil (conductor) circuit shape of the inner layer core board occurs Changes.

When the copper foil of the substrate is removed by etching and the separation of the resin and the ceramic powder is observed, almost only the resin forms a number of streaks toward the edge, and the streaks and streaks come together or separate. When the ceramics are white and the resin is nearly transparent, the separation is observed as streaks of the near-transparent resin in the part of the mixture of the resin and ceramics that looks white. Occasionally, it will be dotted. The streaks are filled with resin and do not form voids. As for the separation of resin and ceramic powder, since the streak-shaped part contains a large amount of resin component, the dielectric constant is lower than that of the other resin-ceramic powder mixture part, causing a variation in the dielectric constant or forming a prepreg. The exposed portion of the surface on the surface of the substrate has a problem of poor appearance and reduced commercial value.

[0007]

The present invention has been made in order to improve this problem, and in a prepreg mainly composed of a thermosetting resin, an inorganic powder and a fiber reinforcing material, it has a high inorganic powder content. A mixture of dielectric constant ceramic powder and fine particle powder having an average particle diameter of 0.1 μm or less is used together.

The term "mainly composed of a thermosetting resin, an inorganic powder and a fiber reinforcing material" means that the prepreg and the substrate are mainly composed of the thermosetting resin, the inorganic powder and the fiber reinforcing material to improve the characteristics of the prepreg and the substrate. Additives, such as flame retardants, antioxidants, colorants, UV absorbers, copper damage inhibitors,
It indicates that a coupling agent, a crosslinking agent, a crosslinking aid, a peroxide, an impact modifier, etc. may be added or reacted.

As the thermosetting resin, a known resin used for a metal-clad laminated substrate can be used, and for example, an epoxy resin, a polyimide resin, a bismaleimide / triazine resin, or a polyester resin can be used. Of these, the epoxy resin, which is widely used, is less colored, and the resin and the ceramic are conspicuously separated by that amount, so that the effect of eliminating the separation of the resin and the inorganic powder according to the present invention is great. Further, the present invention is remarkably effective for resins in which the resin viscosity is largely reduced when heated and melted.

The high dielectric constant ceramic powder of the inorganic powder is added for the purpose of increasing the dielectric constant and has a dielectric constant of 1
It should be 0 or more. The dielectric constant is preferably 50 or more, more preferably 90 or more. Examples of such high dielectric constant ceramics include rutile type titanium dioxide, barium titanate, strontium titanate, calcium titanate, lead titanate, bismuth titanate, barium zirconate, and lead zirconate ceramics. Among these, titanium dioxide, strontium titanate, calcium titanate and a mixture thereof are preferably used, and commercially available high dielectric constant ceramic powder can be used for these. High-dielectric-constant ceramics have a temperature coefficient of +10 to -50 in order to reduce changes in the dielectric constant with temperature.
It is preferable to use ceramics of 00 ppm / ° C.

The addition amount of the high dielectric constant ceramic powder is 50
The amount of up to 300 parts by weight is less than 50 parts by weight, and a large amount of fine particle powder must be added in order to reduce the effect of increasing the dielectric constant and to eliminate separation. If a large amount of fine particle powder is added, the viscosity of the varnish increases and the coatability deteriorates. The amount of 300 parts by weight or less means that the resin cannot fill the voids between the ceramic particles and the amount of the added resin is insufficient to contain the air, and the inclusion of air lowers the dielectric constant and reduces the varnish viscosity. This is because the coating becomes too high to apply.

The average particle diameter of the high dielectric constant ceramics depends on the thickness of the prepreg, but when it is relatively thin, it is 0.3 to
It is preferably 5 μm and the maximum particle size is preferably 10 μm or less. If it is 0.3 μm or less, the specific surface area becomes large and the viscosity of the varnish increases, so that it is impossible to increase the addition amount and the dielectric constant cannot be increased, and if it is physically pulverized to 0.3 μm or less, the cost becomes high. On the other hand, when the thickness is 5 μm or more, the ceramics are easily captured by the fiber reinforcing agent such as glass cloth which causes the separation of the resin and the ceramic powder. When the maximum particle size is 10 μm or more, the metal foil is likely to be captured, and when the metal foil is laminated and press-molded, the metal foil is easily scratched by the ceramics.

The fine particle powder having an average particle diameter of 0.1 μm or less of the inorganic powder is an ultrafine particle powder obtained by a chemical reaction in a liquid phase or a gas phase, and includes hydrous silica of silicon dioxide and anhydrous silica. Anhydrous silica having few silanol groups and good electric properties is preferably used, and commercially available products thereof can be used. Examples of hydrous silica include Nipseal (trade name of Nippon Silica Industry Co., Ltd.), Tokuseal, Fineseal (trade name of Tokuyama Soda Co., Ltd.), Carplex (trade name of Shionogi Pharmaceutical Co., Ltd.), Shilton, Mizukasil (Mizusawa Chemical Co., Ltd.) Industrial Co., Ltd. product name) and Aerosil (Nippon Aerosil Co., Ltd. product name) can be used as anhydrous silica. Further, titanium dioxide fine particle powder titanium dioxide P25
Aluminum oxide C of aluminum oxide (trade name of Nippon Aerosil Co., Ltd.) is preferably used. Further, barium sulfate BF-1 (trade name of Tsuchiya Kaolin Industry Co., Ltd.) and the like are used.

These are 1 to 10% by weight based on 50 to 300 parts by weight of the high dielectric constant ceramic powder.
(0.5-3 with respect to 100 parts by weight of high dielectric constant ceramics
0 parts by weight) is added and used. When the addition amount of the high dielectric constant ceramic powder is large, the addition amount of the fine particle powder is small within the above range, and when the addition amount of the high dielectric constant ceramic powder is small, the addition amount of the fine particle powder is used large. Further, it is better to add a small amount when the specific surface area of the fine particle powder is large, and conversely, add a large amount when the specific surface area is small. Addition amount of fine particle powder is 1
If it is less than wt%, the effect of adding fine particle powder is not obtained,
This is because the addition of 10% by weight or more significantly increases the viscosity of the varnish and makes it impossible to coat the fiber reinforced material such as glass cloth.

The fiber reinforcing material is a glass cloth or a glass non-woven fabric, or a woven or non-woven fabric using polymer fibers such as polyetherimide or aramid fiber, and the glass cloth or the glass non-woven fabric is preferably used. In addition, titanium in the glass composition,
It is possible to use a woven fabric or a non-woven fabric using a fiber whose dielectric constant is increased by adding strontium, calcium, barium, magnesium, zircon, niobium, lead or the like.

[0016]

The function of separating the resin and the high-permittivity ceramic powder occurs when the mixture of the resin and the high-permittivity ceramic powder in the prepreg flows under heat and pressure during press molding.
During press molding, the prepreg is compressed in the thickness direction and flows in the surface direction so that the high-dielectric-constant ceramic powder is captured by the fiber reinforcement such as glass cloth, and the flowable resin under pressure is captured. It is presumed that streaks rich in resin component are generated by breaking through the weak part of the high dielectric constant ceramic powder and flowing.

In a substrate in which copper foils were laminated on both sides of one prepreg and press-molded, the resin and the high-dielectric-constant ceramic powder were separated from each other in the peripheral portion (edge) of the substrate. This is because the part that can largely flow when pressurized is the side surface of the end of the prepreg where the pressure is released, and the resin and high-dielectric-constant ceramic powder flow around the end of the prepreg. It seems to occur. On the other hand, the separation occurrence position in the multilayer board also occurs in the peripheral area of the board, but it also occurs near the center of the board, depending on the shape of the conductor circuit of the inner layer core board, and at that position the resin and high-permittivity ceramic powder flow relatively. It is the part to do.

In addition to the high dielectric constant ceramic powder as the inorganic powder, the thermosetting resin of the present invention has an average particle diameter of 0.1 μm.
When the fine particle powder of m or less is added, when the fine particle powder enters the gaps between the high dielectric constant ceramic particles and the high dielectric constant ceramic particles flow, the high dielectric constant ceramic powder plays a role like a roller and the high dielectric constant ceramic powder is It becomes possible to flow without being captured by the fiber reinforcement. In addition, since the fine particle powder has a large specific surface area and the melt viscosity of the resin increases when it is mixed with the resin, the resin containing the high dielectric constant ceramics flows without being captured by the fiber reinforcing material, so that separation occurs. It is estimated that it will not occur.

When the resin is a thermosetting resin such as an epoxy resin, the resin melts when heated and the viscosity once decreases, and the viscosity increases as the curing reaction proceeds. Since the resin is pressurized when the viscosity is low, the resin flows and easily flows through the gaps between the high dielectric constant ceramic powder particles. When the hardening progresses or when the melt viscosity is high when particles having a large specific surface area are added, it becomes difficult to flow through the gaps between the ceramics and the resistance increases, so that they flow together with the ceramics.

However, since the prepreg is also used for adhesion between the layers of the multi-layer board and has to fill the conductor circuit space of the inner layer core substrate and is required to have the inner layer circuit filling property, too high melt viscosity is not good. When curing progresses and the melt viscosity is high, the fluidity is poor and the inner layer circuit filling property is poor. However, it is unclear what causes it, but when the fine particle powder is added to the resin, the curing reaction slows down, and the melt viscosity of the resin increases only by the amount of the fine particle powder added, and when the fine particle powder is not added It has a relatively low melt viscosity for a while. The addition of the fine particle powder increases the melt viscosity, and the state of this viscosity is maintained for a while due to the delay in the curing time. Flows to fill the inner layer circuit space. It is presumed that the reason why the curing slows down is that the fine particle powder with a large specific surface area adsorbs the curing accelerator, or the peroxide adsorbs the peroxide, or changes the hydrogen ion concentration (pH). .

As described above, by adding the fine particle powder, the particles play a role in the fluidity of the high dielectric constant ceramic powder, increase the viscosity, and slow the curing reaction. It seems that the resin and high-permittivity ceramic powder do not separate, and the inner layer circuit filling property is also excellent.

[0022]

【Example】

Example 1 In a solid content of 1000 g of the epoxy resin varnish shown in Table 1 as a thermosetting resin, strontium titanate-based ceramics SL250 (trade name, average particle diameter by Fuji Titanium Industry Co., Ltd.) as a high dielectric constant ceramics powder among inorganic powders 0.85 μm, maximum particle size 6 μm) 1500 g,
Further, as a fine particle powder having an average particle size of 0.1 μm or less, anhydrous silica Aerosil 200V (trade name of Nippon Aerosil Co., Ltd., average particle size 0.012 μm, specific surface area 2)
(100 m2 / g) (75% (5% by weight based on 1500 g of SL250)) was added, and after stirring, a three-roll mill was passed twice to prepare a varnish in which an inorganic powder was added to the epoxy resin.

This varnish was impregnated with glass cloth (thickness 55 μm, basis weight 47.5 g / m ² ) as a fiber reinforcing material and dried to obtain a prepreg [A] having a thickness of 120 μm. A 18 μm thick copper foil was laminated on both sides of this prepreg [A], heated from room temperature to 170 ° C. at a pressure of 20 kg / cm ² (1.96 MPa), held at 170 ° C. for 90 minutes, and then cooled to around room temperature. Then, a copper-clad laminated substrate was obtained. The copper foil on both surfaces of the substrate was removed by etching, and the thickness of the dielectric was measured. As a result, it was 80 μm. Observation of the surface of this dielectric did not reveal any separation between the epoxy resin and the high dielectric constant ceramic powder. 12G by the cavity resonator method
As a result of measuring the dielectric constant at Hz, it was 12.5.

[0024]

[Table 1]

In order to prepare a multilayer board, a copper foil having a thickness of 35 μm was laminated as an outermost layer as an inner layer core substrate to have a thickness of 0.2 m.
m of the epoxy resin copper-clad laminated board was etched to form a simulated copper foil circuit having a maximum conductor circuit width of 1 mm and a minimum conductor circuit width of 0.1 mm. Using this as an inner layer core substrate, a prepreg [A] and a 18 μm copper foil were laminated on both sides of this substrate and press-molded under the same conditions as above to obtain a four-layer substrate. This substrate was cut at several places, cast-molded with a casting epoxy resin, and then polished and the cross-section of the substrate was observed using a microscope.
As a result, 100 locations were changed, and the copper foil circuit space of the inner layer core substrate was completely filled with the epoxy resin and the inorganic particles in the prepreg and no void was observed, and the inner layer circuit filling property was good.

Examples 2 to 6 and Comparative Examples 1 to 4 Examples 2 to 6 and Comparative Examples 1 to 4 were carried out in the same manner as Example 1 except that the composition was changed, and the results are shown in Table 2. Examples 2 and 3 are examples in which the addition amounts of the high dielectric constant ceramic powder were 50 parts by weight and 200 parts by weight, respectively, and the addition amounts of the fine particle powders were 10% by weight and 1% by weight, respectively. As in Example 1, there was no separation, and the inner layer circuit filling property was excellent. Examples 4, 5
Is a case where the fine particle powder of Example 1 was changed to another particle, and titanium dioxide P25 (trade name of Nippon Aerosil Co., Ltd., average particle diameter 0.021 μm, specific surface area 5)
0m ² / g) high dielectric constant ceramic powder SL250
5 wt% and 10 wt% were added to 150 parts by weight. Both the separation and the inner layer circuit filling property were good.

In Example 6, the fine particle powder Aerosil 200V of Example 1 was added and mixed in an amount of 1% by weight with respect to 150 parts by weight of SL250, but slight separation was observed. However, there was a remarkable difference as compared with Comparative Example 2 in which the fine particle powder was not added. In Comparative Example 1, no inorganic powder was added, which was the same as a normal epoxy resin substrate, and the separation and inner layer circuit fillability were good. Comparative Example 3 is a case where 20% by weight of fine-particle powder titanium dioxide P25 was added. Separation did not occur, but the inner layer circuit filling property was deteriorated.

In Comparative Example 4, Aerosil 200V is SL2.
This is the case where 15% by weight is added to 50 150 parts by weight. High dielectric constant ceramic powder S on epoxy resin varnish
When L250 and Aerosil 200V were gradually added, the solvent in the varnish was absorbed by these particles and the varnish became a gel so that the glass cloth could not be coated. The prepreg obtained by applying a varnish forcibly by adding a large amount of solvent has a mixture of epoxy resin and inorganic particles peeled from the glass cloth in some places, and the prepreg is cut to a specified size with a cutter. Even when it was carried out, it fell off from the glass cloth into powder and could not be used as a prepreg.

[0029]

[Table 2]

When the gelling time was measured at 170 ° C. for the varnishes of Examples 1 and 2 and Comparative Examples 2 and 3, Comparative Example 1
In the formulation that does not add inorganic particles to the epoxy resin of,
In 7 minutes and 11 seconds, the high dielectric ceramic SL2 of Comparative Example 2
In the formulation in which 150 parts by weight of 50 was added, it was slightly delayed in 7 minutes and 20 seconds, but in Example 1 in which 5% by weight of fine particle Aerosil 200V was added to the formulation of Comparative Example 2, 13 minutes and 10 minutes.
It was late for a second. Aerosil 200V 10% by weight
In the added example 2, the time was delayed to 21 minutes and 30 seconds.

By adding the fine particle powder having an average particle diameter of 0.1 μm or less, the melt viscosity of the resin is high, and the curing speed is slow, so that it becomes slow to fill the conductor circuit space of the inner core substrate. In addition, it is thought that even if the viscosity is high, it can flow, and by entering into the gaps of the high dielectric constant ceramic particles and acting like a roller, the fluidity is increased and the separation and the inner layer circuit filling property are remarkably improved.

If the curing speed is only slowed down, it is sufficient to reduce the amount of the curing accelerator. In Comparative Example 2, the amount of the curing accelerator was reduced and the gelling time was 10 minutes and 30 seconds. There has occurred. It seems that it is not only the effect of curing time. Further, 50 parts by weight of titanium dioxide having an average particle size of 0.44 μm was further added to Comparative Example 2, but separation occurred.

[0033]

As shown in Examples and Comparative Examples, the dielectric constant is increased by adding a high dielectric constant ceramic powder as an inorganic powder and a fine particle powder having an average particle diameter of 0.1 μm or less to a thermosetting resin. Moreover, it is possible to obtain a prepreg or a substrate having a good inner layer circuit filling property without separating the thermosetting resin and the high dielectric constant ceramic powder. As a result, it is possible to manufacture a multilayer board or substrate having a uniform dielectric constant, a good appearance, and no blister or delamination in the soldering process or the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B32B 27/38 7421-4F C08K 3/34 C08L 63/00 NKX // B29K 63:00 105: 06 309: 02 (72) Inventor Katsuhiro Onose 48 Wadai, Tsukuba-shi, Ibaraki Hitachi Chemical Co., Ltd. Tsukuba Development Laboratory (72) Inventor Harumi Negishi Haruka, Ibaraki Ogawa 1500 Oita Hitachi Chemical Co., Ltd. Shimodate in the factory

Claims (4)

[Claims] 1. In a prepreg composed mainly of a thermosetting resin, an inorganic powder and a fiber reinforcement, a high dielectric constant ceramic powder and a fine particle powder having an average particle diameter of 0.1 μm or less are used as the inorganic powder. High-permittivity prepreg characterized by. 2. High-dielectric-constant ceramic powder is 50 to 300 parts by weight with respect to 100 parts by weight of thermosetting resin, and fine particle powder having an average particle diameter of 0.1 μm or less is added to the high-dielectric-constant ceramic powder. 1 to 10% by weight of the high dielectric constant prepreg according to claim 1. 3. The high dielectric constant prepreg according to claim 1, wherein the thermosetting resin is an epoxy resin. 4. A laminated board using the high dielectric constant prepreg according to claim 1.